Perinatal lesions of the developing hippocamus (Sommer's sector of Ammon's Horn) have commonly been associated with neurologic disabilities in both childhood and adult life that include emotional instability, memory deficits, and partial complex seizures. This rather large group of disorders, which has been ascribed to the selective vulnerability of the hippocampus during development, is associated with relatively minor pathologic changes ("Sclerosis of Ammon's Horn"). We have previously shown that alterations of cerebral insocortex can occur that are more quantitative than qualitative; i.e. a disturbance of the differentiation of neurons, the development and myelination of their interconnecting fibers, and the distribution of associated glial cells. In the present studies, the focus will be on similar disorders of "structural disorganization" of the hippocampal formation; such disorders have been difficult to approach with routine neuropathologic methods. We propose to show that quantitative histochemistry can result in useful pathologic study and clinco-pathologic correlation that will lead new concepts of mechanisms involved in perinatal damage and recovery of function of the developing hippocampus. Research aims include surveying the biochemical architecture of the hippocampal formation (CA1 hippocampus and ventral limb of dentate gyrus) in rat during postnatal maturation, by employing principles and methods of quantitative histochemistry. Performing microchemical analyses of rat hippocampal formation (including laminar histochemical profiles of the adult structure) choosing a carefully selected group of biochemical compounds which have previously been shown capable of documenting quantitative developmental and pathologic changes with respect to neurons, glia, nyelin, axodendritic preocesses and synapses (cholinergic and gabaminergic). Assessing the microchemical pathology of high dose corticosteroid treatment during early postnatal life on developing hippocampal formation of the rat and derive principles of experimental neuropathology at given stages of hippocampal maturation that can be applied to neurological problems in man (such as memory difficulties, hyperactive behavior, complex partial seizures, etc.).